GATE EC 2015 Set 2 — Question 19
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Electronic Devices → Carrier Transport → Generation & Recombination
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Question
An n-type silicon sample is uniformly illuminated with light which generates electron-hole pairs per per second. The minority carrier lifetime in the sample is . In the steady state, the hole concentration in the sample is approximately , where is an integer. The value of is ______.
Correct answer
14 to 14
Solution
In steady state, the generation rate () equals the recombination rate (). The excess hole concentration () is given by the product of the generation rate and the minority carrier lifetime:Given:
In an n-type semiconductor, the total hole concentration is . Since the sample is illuminated such that a high concentration of excess carriers is generated, is much larger than the equilibrium hole concentration . Thus, .
Comparing this with the given form , we find .
In an n-type semiconductor, the total hole concentration is . Since the sample is illuminated such that a high concentration of excess carriers is generated, is much larger than the equilibrium hole concentration . Thus, .
Comparing this with the given form , we find .
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